The ability of statins to lower plasma lipid levels and the possible changes in the blood rheology and fibrinolysis were studied in 29 patients with type II A hypercholesterolemia. Fourteen patients received Simvastatin (Zocor, MSD) and 15- Pravastatin (Elisor, Squibb) both by 20 mg with the evening meal. TC and Tg were measured with enzyme methods, HDL-C - after precipitation with dextran-sulfate magnesium and LDL-C was calculated. Apo AI and apoB were determined with immunoturbidimetric method. Plasminogen, α 2 AP and FXIII were measured with RID. Fibrinogin was assessed with chronometric Multifibren kits. Plasma viscosity was measured with capillary viscosimeter. After 8 weeks TC and LDL-C decreased significantly in both groups. Hct was significantly lower after treatment with Simvastatin and plasminogen, apoAI and FXIII-after treatment with Pravastatin. Plasma viscosity was lower after Simvastatin, but not after Pravastatin. Fibrinogen and α 2 Ap were not altered. We found a positive correlation between plasma viscosity/TC(p < 0,1) and plasma viscosity/ LDL-C(p < 0,1). Simvastatin and Pravastatin showed a good lipid-lowering effect even in a short treatment course (8 weeks). Pravastatin has additional beneficial effect on the coagulation and fibrinolysis.